OBJECTIVES: (1) To understand the mechanism of packaging of bacteriophage lambda chromosomes, including the basis of lambda DNA recognition, the basis of polarized packaging into the capsid, and DNA length requirements for packaging. METHODS: (1) Standard genetic techniques, particularly those employed in our previous work. (2) Mutational analysis of the cohesive end site utilizing in vivo and in vitro approaches. (3) Comparative studies with natural variants related to lambda. BIBLIOGRAPHIC REFERENCES: Feiss, Michael, R.A. Fisher, M.A. Crayton and Carol Egner. 1977. Packaging of the Bacteriophage Lambda Chromosome: Effect of Chromosome Length. Virology 77:281-293. Sunshine, M., M. Feiss, J. Stuart and J. Yochem. A new host gene (groPC) necessary lambda DNA replication. Molecular and General Genetics 151:27-34.